Pre-stressed fiber reinforcing member and method for its manufacture

ABSTRACT

A composite structural article (100) includes a polymeric body (35) having a first major surface (24) and an opposing second major surface (22) and a rib element (30) extending away from the first major surface. A reinforcing member (10) is embedded within a free end portion (34) of the rib member (30). The reinforcing member includes an elongated polymer rod having a rod length and a plurality of co-extending continuous fibers (20), embedded and distributed within the elongated polymer rod. The fibers are under tension and may have a helical or twisted configuration along the rod length.

This application is the § 371 U.S. National Stage of InternationalApplication No. PCT/US16/17519, filed 11 Feb. 2016, which claims thebenefit of U.S. Provisional Application No. 62/115,409, filed 12 Feb.2015, the disclosures of which are incorporated by reference herein intheir entireties.

BACKGROUND

The physical properties of thermoplastic polymers can be improved by theincorporation of filler materials such as glass fibers. Theincorporation of reinforcing material, such as glass fiber, intopolymeric products beneficially affects resin properties such as tensilestrength, stiffness, dimensional stability and resistance to creep andthermal expansion. Traditional methods of producing such articles havebeen injection molding or compression molding standard, pre-compoundedfiber glass reinforced polymer. While satisfying certain objectives inoptimizing the quality of the finished product, conventional filledproducts have proven to be commercially costly and in other ways havefallen short of their objectives in terms of weight, impact performanceand strength. Improvements to producing fiber reinforced articles aredesired.

SUMMARY

The present disclosure relates to a pre-stressed fiber reinforcingmember and methods of making the same. The pre-stressed fiberreinforcing member can improve the structure properties while reducingthe weight and/or cost of the composite structural article. Thepre-stressed fiber reinforcing member may include a plurality ofcontinuous fiber placed in or under tension within the reinforcingmember.

In one aspect, a reinforcing member includes an elongated polymer rodextending between a proximal (first) end and a distal (second) end. Aplurality of co-extending continuous fibers are embedded and distributedwithin the elongated polymer rod. The plurality of co-extendingcontinuous fibers form a helix or twisted configuration from theproximal end to the distal end. The reinforcing member may include aresin or polymer skin layer having substantially no co-extendingcontinuous fibers and a concentration of co-extending continuous fibersincreases as towards a longitudinal axis of the elongated polymer rod.

In another aspect, a method includes the steps of coating a plurality ofco-extending continuous fibers with a thermoplastic polymer to formcoated continuous fibers and forming the coated continuous fibers intoan elongated polymer rod. Then the method includes spiral winding ortwisting the co-extending continuous fibers to form a pre-stressed fiberreinforcing member having a fiber helix within the elongated polymerrod.

The method may further include embedding the pre-stressed fiberreinforcing member into a polymeric body to form a composite structuralarticle. The composite structural article may include a polymeric bodyhaving a first major surface and an opposing second major surface, andthe pre-stressed fiber reinforcing member is embedded within thepolymeric body.

The composite structural article may include a polymeric body having afirst major surface and an opposing second major surface and a ribelement extending away from the first major surface and extending alongthe first major surface a length value. The rib element has an attachedportion fixed to the first major surface and an opposing free endportion. A pre-stressed fiber reinforcing member is embedded within theopposing free end portion of the rib. The reinforcing member includes anelongated polymer rod having a rod length and a plurality ofco-extending continuous fibers, under tension and embedded anddistributed within the elongated polymer rod. The fibers may have ahelical or twisted configuration along the rod length.

These and various other features and advantages will be apparent from areading of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which:

FIG. 1 is a side elevation schematic diagram view of an illustrativepre-stressed fiber reinforcing member;

FIG. 2 is a side elevation schematic diagram view of anotherillustrative pre-stressed fiber reinforcing member having a texturedsurface;

FIG. 3 is a schematic diagram of a method of forming an illustrativepre-stressed fiber reinforcing member;

FIG. 4 is a cross-sectional schematic diagram view of an illustrativecomposite structural article including the pre-stressed fiberreinforcing member; and

FIG. 5 is a perspective view of a container formed of compositestructural articles including pre-stressed fiber reinforcing memberdescribed herein.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which are shown byway of illustration several specific embodiments. It is to be understoodthat other embodiments are contemplated and may be made withoutdeparting from the scope or spirit of the present disclosure. Thefollowing detailed description, therefore, is not to be taken in alimiting sense.

All scientific and technical terms used herein have meanings commonlyused in the art unless otherwise specified. The definitions providedherein are to facilitate understanding of certain terms used frequentlyherein and are not meant to limit the scope of the present disclosure.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the properties sought tobe obtained by those skilled in the art utilizing the teachingsdisclosed herein.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, and 5) and any range within that range.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise.

As used in this specification and the appended claims, the term “or” isgenerally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

As used herein, “have”, “having”, “include”, “including”, “comprise”,“comprising” or the like are used in their open ended sense, andgenerally mean “including, but not limited to”. It will be understoodthat “consisting essentially of”, “consisting of”, and the like aresubsumed in “comprising,” and the like.

It should be noted that “top” and “bottom” (or other terms like “upper”and “lower” or “first” and “second”) are utilized strictly for relativedescriptions and do not imply any overall orientation of the article inwhich the described element is located.

The phrase “pre-stressed” refers to a configuration where a fiber is inor under tension within a polymeric rod and the fiber may be twisted ordisposed in a helical configuration along the length of the polymericrod.

The present disclosure relates to a pre-stressed fiber reinforcingmember and methods of making the same. The pre-stressed reinforcingfiber member can improve the structural properties while reducing theweight and/or cost of the composite structural article. The pre-stressedfiber reinforcing member can be placed strategically within thepolymeric body to provide strength where it is needed within thepolymeric body. The pre-stressed fiber configuration provides an unusualor surprising increase in the tensile strength of these reinforcingmembers as compared to reinforcing members that are not pre-stressed. Inparticular, these pre-stressed fiber reinforcing members include aplurality of co-extending continuous fibers that are in tension withinthe polymer rod and the plurality of co-extending continuous fibers.These composite structural articles possess a high strength, stiffness,and high impact resistant with a reduced weight as compared toconventional structural articles. While the present disclosure is not solimited, an appreciation of various aspects of the disclosure will begained through a discussion of the examples provided below.

FIG. 1 is a side elevation schematic diagram view of an illustrativepre-stressed fiber reinforcing member 10. The reinforcing member 10includes an elongated polymer rod 12 extending between a proximal(first) end 11 and a distal (second) end 13, and a plurality ofco-extending continuous fibers 20, embedded and distributed within theelongated polymer rod 12, and forming a helix or twisted configurationfrom the proximal end 11 to the distal end 13. The helical continuousfibers 20 are preferably under tension within the reinforcing member 10,providing a “pre-stressed” fiber reinforcing member 10.

The pre-stressed fiber reinforcing member 10 can be formed by applying atension to the plurality of co-extending continuous fibers 20 (that areembedded and distributed within the elongated polymer rod 12) while theelongated polymer rod 12 is still in a molten or softened state and thentwisting the proximal (first) end 11 relative to the distal (second) end13 to form a twisted fiber configuration. Once in this twisted fiberconfiguration, and under tension, the elongated polymer rod 12 can becooled or solidified to lock in the stress or tension of theco-extending continuous fibers 20. This configuration may be referred toas the “pre-stressed” fiber reinforcing member.

In many embodiments the co-extending continuous fibers 20 are notuniformly distributed throughout a cross-section of the elongatedpolymer rod 12 and may concentrate towards the longitudinal axis of theelongated polymer rod 12. This may occur due as the fibers are twisted.In many of these embodiments a skin layer of polymer (that forms thepolymeric body) may form on the outer surface of the pre-stressed fiberreinforcing member 10 where there is no co-extending continuous fibers20. This skin layer may form 10% or less or from 1 to 10% of thediameter of the pre-stressed fiber reinforcing member 10. In someembodiments the co-extending continuous fibers 20 are uniformlydistributed throughout a cross-section of the elongated polymer rod 12.

Polymer material “wets out” the co-extending continuous fibers 20. Thusresin or polymeric material is dispersed about all of the co-extendingcontinuous fibers 20. The reinforcing member 10 can include at least1000, or at least 5000, or at least 10000 or at least 15,000co-extending continuous glass fibers.

The continuous fibers 20 can be formed of any suitable fiber materialproviding tensile strength and/or stiffness. The continuous fibers 20can be composed of: glass, carbon, graphite, basalt, DuPont Kevlar brandaramid fibers (i.e., poly-paraphenylene terephthalamide), ceramics,natural fibers, polymeric fibers, and various metals. Preferably thecontinuous fibers 20 are composed of glass, carbon, graphite or Kevlar(i.e., poly-paraphenylene terephthalamide) fibers. In some embodimentsthe continuous fibers 20 are a mixture of glass and carbon fibers orglass and Kevlar fibers or glass and graphite fibers.

The continuous fibers 20 can have any suitable diameter such as 5 to 100micrometers or less than 50 micrometers or from 5 to 50 micrometers orfrom 5 to 30 micrometers, or from 5 to 20 micrometers, or from 7 to 15micrometers. The continuous fiber 20 can have any suitable length andpreferably extends the entire lateral length of the reinforcing member10. In many embodiments the continuous fiber 20 has a length of at least0.1 meter, or 0.5 meter or 1 meter or greater than 1 meter.

The reinforcing member 10 can have a diameter or largest lateraldimension in a range from 250 to 10000 micrometers or from 500 to 5000micrometers or from 1000 to 5000 micrometers or less than 10 mm or lessthan 5 mm. The reinforcing member 10 can have at least 40% wt fiber orat least 50% wt fiber or from 40 to 90% wt fiber or from 50 to 80% wtfiber. Each continuous fiber element can have at from 60 to 10% wtpolymer or from 50 to 20% wt polymer.

The reinforcing member 10 can have any useful cross-sectional shape. Inmany embodiments the reinforcing member 10 has a circular or ovalcross-sectional shape. In other embodiments the reinforcing member 10has a polygon cross-sectional shape.

The polymer forming the reinforcing member 10 can be any suitablepolymeric material. In many embodiments the polymeric material is athermoplastic material. Useful polymeric material includespolypropylene, polyethylene, nylon, acrylonitrile butadiene styrene,styrene acrylonitrile, acrylic or styrene, for example. Further usefulpolymers include PBT polyester, PET polyester, polyoxymethylene,polycarbonite or polyphenylene sulfide for example. Higher temperaturepolymeric material includes polysulfone, polyethersulfone,polyethereetherketone, or liquid crystal polymer, for example.

In some embodiments a skin layer or skin region of polymer material(outer polymer layer 26 illustrated in FIG. 4) surrounds the pluralityof co-extending continuous fibers 20 having a helical or twistedconfiguration. This skin layer or skin region can be free of fibermaterial or have less than 10% or less than 5% fiber material or is freeof fiber material (both continuous fiber and fiber dispersion).Preferably the skin layer or skin region is free of the plurality ofco-extending continuous fibers 20 having a helical or twistedconfiguration. The skin layer or skin region can have any usefulthickness such as 25 micrometers to 1000 micrometers or from 50 to 500micrometers or from 250 to 500 micrometers.

The reinforcing member 10 has a core region that includes the pluralityof co-extending continuous fibers 20 in tension. The skin layer or skinregion may surround the core region. The core region may be a fiberconcentration of at least 40% wt or from 40% wt to 90% wt or from 50% wtto 90% wt. The fiber concentration may increase towards the center orlongitudinal axis of the reinforcing member.

The plurality of co-extending continuous fibers having a helical ortwisted configuration can have any useful period or distance for acomplete rotation along the reinforcing member 10 or rod length. Thehelical period may be in a range of at least about 5 cm, or at least 10cm, or at least 20 cm, or at least 30 cm. In many embodiments thehelical period is in a range from about 5 cm to 50 cm or from 5 cm to 30cm or from 5 cm to 20 cm.

FIG. 2 is a side elevation schematic diagram view of anotherillustrative pre-stressed fiber reinforcing member 10 having a texturedsurface 15. Adding texture 16 to the outer surface 14 of the elongatedpolymer rod 10 can increase the outer surface area and improve adhesionto a polymeric body when forming a composite structural article. Thetexture 16 can include ridges or valleys imprinted into the outersurface 14 of the elongated polymer rod 10. The term “textured” refersto a surface having uniform or non-uniform undulating surface or peaksand valleys along the surface. The texture may assist in holding thepre-stressed fiber reinforcing member in place during the moldingprocess of a composite article. The texture may assist in centering thepre-stressed fiber reinforcing member in a mold cavity during themolding process of a composite article.

In many embodiments the texture 16 increases a surface area of the outersurface 14 by at least 5% or at least 10% or at least 20%. In oneexample, the textured surface 15 is formed by knurling the outer surface14 of the elongated polymer rod 10. The texture can be formed by anyuseful process, such as embossing or over-molding for example.

FIG. 3 is a schematic diagram of a method 101 of forming an illustrativepre-stressed fiber reinforcing member 10. Once formed, the pre-stressedfiber reinforcing member 10 can then be embedded into a polymeric bodyto provide reinforcement properties to a composite polymeric body.

Fiber spools 120 provide a bundle of continuous fiber to an extruder die134. The bundle of continuous fiber can each include a plurality ofcontinuous fibers such as at least, 1000 fibers, or at least 2500 fibersor at least 5000 fibers. The extruder 132 extrudes polymer to the die134 and the continuous fibers 20 pass through the die and “wets out”each continuous fiber with the resin or polymer. The extruder die 134embeds the bundle of continuous fiber within resin or polymer materialand forms a plurality of continuous coated fiber elements 125. Thesecontinuous coated fiber elements 125 can be guided together to form anelongated polymer rod 12 and spiral wound or twisted to form apre-stressed fiber reinforcing member 10 having a fiber helix within theelongated polymer rod.

The spiral winding or twisting of the continuous coated fiber elements125 can be provided downstream of the die 134. A puller/twister 102 caninduce tension within the continuous fibers 20 embedded within themolten or semisolid polymer rod and may also induce a twist or helicalconfiguration of the continuous fibers 20 embedded within the molten orsemisolid polymer rod. The puller/twister 102 can impart any level oftwist desired to the pre-stressed fiber reinforcing member 10 within theelongated polymer rod 12. The elongated polymer rod 12 can be cooled orsolidified to lock in the stress or tension of the co-extendingcontinuous fibers 20. This configuration may be referred to as the“pre-stressed” fiber reinforcing member.

The pre-stressed fiber reinforcing member 10 can pass though pullerelement 102 and be diced or cut (with a knife 104, for example) to anappropriate size to form the reinforcing member 10 described herein. Thecut reinforcing member 10 can then be embedded into a polymeric body toform a composite structural article by injection molded or molding.

FIG. 4 is a cross-sectional schematic diagram view of an illustrativecomposite structural article 100 including the pre-stressed fiberreinforcing member 10. The composite structural article 100 includes apolymeric body 35 having a first major surface 24 and an opposing secondmajor surface 22, and a pre-stressed fiber reinforcing member 10,described herein, embedded within the polymeric body 35.

In many embodiments, the polymeric body 35 includes a laterallyextending rib member 30 extending away from the first major surface 24and having a lateral length or length value and forming a portion of thepolymeric body 35. The reinforcing member 10 extends along the laterallength or length value and is embedded within the rib member 30. In manyembodiments the rib element length is coextensive with the reinforcingmember rod length or the rib element length is substantially equal withthe reinforcing member rod length.

The rib element 30 may extend away from the first major surface 24 andextending along the first major surface 24 a length value. The ribelement 30 includes an attached portion 32 fixed to the first majorsurface 24 and an opposing free end portion 34. The reinforcing member10 is embedded within the opposing free end portion 34. As describedabove, the reinforcing member 10 includes an elongated polymer rodhaving a rod length and a plurality of co-extending continuous fibers20, embedded and distributed within the elongated polymer rod. Thefibers 20 having a helical or twisted configuration along the rodlength. The illustrative composite structural article 100 has a single,or only one, or less than two pre-stressed fiber reinforcing member 10per rib element 30.

The reinforcing member 10 may include a skin layer 26 of polymermaterial surrounding the plurality of co-extending continuous fibers 20having a helical or twisted configuration. In many embodiments the skinlayer 26 is formed of the same type of polymer material as the polymermaterial dispersing the plurality of co-extending continuous fibers 20,embedded and distributed within the elongated polymer rod.

In many embodiments, the rib element 30 opposing free end portion 34defines a curved or rounded end surface 14. In these embodiments, thereinforcing member 10 may define the curved or rounded end surface 14.This may be particularly useful when the reinforcing member 10 is moldedonto or into the rib element 30 of the composite structural article 100.

At least 50% of an outer surface area of the reinforcing member 10 maybe fixed to the solid or polymeric body 35 or rib element 30. Thereinforcing member 10 may have less than 90% of the outer surface areaof the reinforcing member 10 fixed to the solid or polymeric body 35 orrib element 30. The reinforcing member 10 may have from 50% to 90% ofthe outer surface area of the reinforcing member 10 fixed to the solidor polymeric body 35 or rib element 30. FIG. 4 illustrates that about50% to 75% of the outer surface area of the reinforcing member 10 isfixed to the solid or polymeric body 35 rib element 30 distal or freeend 34.

The solid or polymeric body 35 can be formed of any suitable polymericmaterial. In many embodiments the polymeric material is a thermoplasticmaterial. Useful polymeric material includes polypropylene,polyethylene, nylon, acrylonitrile butadiene styrene, styreneacrylonitrile, acrylic or styrene, for example. Further useful polymersinclude PBT polyester, PET polyester, polyoxymethylene, polycarbonite orpolyphenylene sulfide for example. Higher temperature polymeric materialincludes polysulfone, polyethersulfone, polyethereetherketone, or liquidcrystal polymer, for example.

In many embodiments the polymer utilized to form the pre-stressed fiberreinforcing member 10 is compatible with, or is the same type or kindof, polymer material forming the solid or polymeric body of thecomposite structural element 35. In other embodiments the polymerutilized to form the pre-stressed fiber reinforcing member 10 is adifferent type or kind of polymer material. In some embodiments thepolymer utilized to form the pre-stressed fiber reinforcing member 10 isa homopolymer and the polymer material forming the solid or polymericbody of the composite structural element 35 is a copolymer. In otherembodiments the polymer utilized to form the pre-stressed fiberreinforcing member 10 is a copolymer and the polymer material formingthe solid or polymeric body of the composite structural element 35 is ahomopolymer.

In many embodiments a plurality of fibers form a fiber dispersion withinthe polymeric body 35. The fibers forming this fiber dispersion have anaverage length of less than 15 mm and an average diameter of less than50 micrometers. The polymeric material forming the solid or polymericbody 35 can includes a plurality of random fibers forming a fiberdispersion in the polymeric material. This fiber dispersion has anaverage fiber length of less than 15 mm or less than 12 mm or less than5 mm or less than 1 mm. The fiber dispersion has an average fiber lengthin a range from 1 to 15 mm or in a range from 5 to 12 mm and can betermed “long fiber thermoplastic”. In other embodiments, the fiberdispersion has an average fiber length in a range from 0.1 to 1 mm or ina range from 0.25 to 0.75 mm and can be termed “short fiberthermoplastic”.

The fibers forming the fiber dispersion can be formed of materials thatare the same or different than the material forming the continuousfibers 20 such as glass, carbon, basalt, graphite, DuPont Kevlar brandaramid fibers, ceramics, natural fibers, polymeric fibers, and variousmetals, for example. Preferably fibers forming the fiber dispersion canbe composed of glass, carbon, graphite or Kevlar (i.e.,poly-paraphenylene terephthalamide) fibers. In some embodiments thefibers forming the fiber dispersion are a mixture of glass and carbonfibers or glass and Kevlar fibers or glass and graphite fibers. In someembodiments the fibers forming the fiber dispersion is glass and thefibers forming the continuous fibers 20 are carbon, Kevlar or graphiteor a mixture of glass and carbon, Kevlar or graphite.

The fiber dispersion can be present in the polymeric material of thesolid or polymeric body 35 can be in a range from 5 to 60% by weight.Preferably the fiber dispersion can be present in the polymeric materialin a range from 10 to 50% by weight, or in a range from 20 to 45% byweight, or in a range from 30 to 40% by weight. Useful polymericmaterial with fiber dispersions are commercially available from RTPCompany, Winona, Minnesota under the trade designations “RTP 107”(polypropylene with 40% wt short glass fiber dispersion) and “RTP 80107”(polypropylene with 40% wt long glass fiber dispersion), for example.

In many embodiments, the pre-stressed fiber reinforcing member 10 doesnot include, or is free of the fiber dispersion that is present in thesolid or polymeric body 35. In many embodiments the reinforcing member10 skin layer 26 does not include, or is free of the fiber dispersionthat is present in the solid or polymeric body 35.

FIG. 5 is a perspective view of a container 200 formed of compositestructural articles including the twisted or pre-stressed fiberreinforcing member described herein. The container 200 is formed of atleast four composite structural panels 210. Each composite structuralpanel or side of the container 200, includes one or more pre-stressedfiber reinforcing members 10 embedded in ribs 30 that extend away fromthe first major surface 24.

In this embodiment, a second major surface 22 is planar and an opposingfirst major surface 24 includes a plurality of intersecting rib elements30 that extend away from the first major surface 24. A first pluralityof parallel rib elements extend along a length of the panel member and asecond plurality of parallel rib elements extend along a width of thepanel members. The first plurality of rib elements intersect and areorthogonal to the second plurality of rib elements. One or morepre-stressed fiber reinforcing members 10 may be embedded in each rib30, preferably along a distal end portion of the rib 30 (as illustratedin FIG. 4).

In some embodiments, an open mesh woven element 40 can be embeddedwithin the second major surface 22 and formed of any suitable fibermaterial providing tensile strength and/or stiffness in two orthogonaldirections and impact resistance. The open mesh woven element 40 can beformed of a plurality of first parallel fibers extending in a firstdirection in a plane and a plurality of second parallel fibers extendingin a second direction (orthogonal to the first direction) in the plane.The first plurality and second plurality of fibers can be composed of:glass, basalt, carbon, graphite, DuPont Kevlar brand aramid fibers,ceramics, natural fibers, polymeric fibers, and various metals. The openmesh woven element 40 can impart impact resistance and strengthen thecomposite structural panels 210.

The composite structural article can be formed by any suitable method.In many embodiments the pre-stressed fiber reinforcing member can beplaced in a suitable mold and the polymeric material disposed into themold to form the composite structural article. Preferably the compositestructural articles are formed by inserting the pre-stressed fiberreinforcing member in a mold and polymer material is compression moldedor injection molded about the pre-stressed fiber reinforcing member.

The pre-stressed fiber reinforcing member described herein can beutilized in structural composite articles for a variety of industries,markets and applications. The composite articles described herein areparticularly useful for: automotive parts such as bumpers, fenders;transportation such as pallets and containers; aerospace such asairplane components; military such as missile components; recreationsuch as vehicle frame components.

One illustrative example provided three polypropylene composite panelsfor testing. The first was a control sample (C) that consisted ofpolypropylene and 40% wt glass fiber dispersion (long glass fibers orLFT) with no reinforcing member. A second sample (1) was the samepolypropylene and 40% wt glass fiber dispersion with a non-twisted (notpre-stressed) reinforcing member (4000 filaments at about 15 micrometerin diameter). The final sample (2) was the same polypropylene and 40% wtglass fiber dispersion with a pre-stressed (twisted) fiber reinforcingmember (with 4000 filaments at about 15 micrometer in diameter).

These samples were subjected to flexural testing. The control sample (C)had a test result of 477 pounds to failure. The first sample (1) had atest result of 1506 pounds to failure. The second sample (2) had a testresult of 1758 pounds to failure. It is surprising that by simplypre-stressing or twisting the reinforcing member the structuralproperties would increase as much as was shown.

One exemplary composite structural article includes a polymeric bodyformed of a polypropylene copolymer and filled with about 20% wt long orshort glass fiber. The single pre-stressed fiber reinforcing member isembedded within a free end of a rib element of the polymeric body. Thepre-stressed fiber reinforcing member has a diameter of about 5 mm andincludes about 16,000 continuous glass fibers (each fiber having adiameter of about 15 micrometers) dispersed in polypropylenehomopolymer. The pre-stressed (twisted or helical configuration alongthe length of the reinforcing member) fiber reinforcing member has anouter polymer region or skin layer (that is substantially free ofcontinuous glass fibers or fiber dispersion) that is about 250 to 500micrometers thick. The filled polypropylene copolymer is injectionmolded onto the pre-stressed fiber reinforcing member. The pre-stressedfiber reinforcing member forms a curved portion of a free end of a ribmember extending from the composite structural article.

Thus, embodiments of PRE-STRESSED FIBER REINFORCING MEMBER aredisclosed.

All references and publications cited herein are expressly incorporatedherein by reference in their entirety into this disclosure, except tothe extent they may directly contradict this disclosure. Althoughspecific embodiments have been illustrated and described herein, it willbe appreciated by those of ordinary skill in the art that a variety ofalternate and/or equivalent implementations can be substituted for thespecific embodiments shown and described without departing from thescope of the present disclosure. This application is intended to coverany adaptations or variations of the specific embodiments discussedherein. Therefore, it is intended that this disclosure be limited onlyby the claims and the equivalents thereof. The disclosed embodiments arepresented for purposes of illustration and not limitation.

What is claimed is:
 1. A composite structural article comprising: apolymeric body having a first major surface and an opposing second majorsurface; a rib element extending away from the first major surface andextending along the first major surface a length value, the rib elementhaving an attached portion fixed to the first major surface and anopposing free end portion; and a reinforcing member embedded within theopposing free end portion; the reinforcing member comprising: anelongated polymer rod having a rod length; and a plurality ofco-extending continuous fibers, embedded and distributed within theelongated polymer rod, and fibers having a helical or twistedconfiguration along the rod length.
 2. The article according to claim 1,wherein the plurality co-extending continuous fibers comprise at least1000 glass fibers, carbon fibers or poly-paraphenylene terephthalamidefibers.
 3. The article according to claim 1, wherein the reinforcingmember comprises 40-90% wt fiber and 60-10% wt polymer.
 4. The articleaccording to claim 1, wherein the reinforcing member comprises an outerpolymer layer surrounding the plurality of co-extending continuousfibers.
 5. The article according to claim 1, further comprising aplurality of fibers forming a fiber dispersion within the polymericbody, the fibers having an average length of less than 15 mm, and anaverage diameter of less than 50 micrometers and the polymeric bodycomprises 10% to 50% by weight fiber dispersion.
 6. The articleaccording to claim 5, wherein the fiber dispersion is not present withinthe reinforcing member.
 7. The article according to claim 1, wherein theelongated polymer rod has an outer surface comprising texture.
 8. Thearticle according to claim 1, wherein the plurality of co-extendingcontinuous fibers increase in concentration towards a longitudinal axisof the elongated polymer rod.
 9. The article according to claim 1,wherein the rib element length and the reinforcing member rod length andthe plurality of co-extending continuous fibers are coextensive.
 10. Thearticle according to claim 5, wherein the plurality of co-extendingcontinuous fibers and the fibers forming a fiber dispersion aredifferent types of fiber.
 11. The article according to claim 1, whereinthe reinforcing member comprises 50-80% wt glass fiber and 50-20% wtpolymer.
 12. The article according to claim 1, wherein the plurality ofco-extending continuous fibers comprise a helical configuration and hasat least one complete rotation along the rod length.
 13. The articleaccording to claim 11, wherein the plurality of co-extending continuousfibers increase in concentration towards a longitudinal axis of theelongated polymer rod.